In a related radio wave sensor (high frequency sensor), it has been known to use radio waves as one of wireless media (for example, JP 2007-104027 A (hereinafter referred to as “Document 1”)). The radio wave sensor described in Document 1 includes a transmitting antenna and a receiving antenna that are mounted on a substrate with a space between them, and a housing (dielectric lens) that is disposed forward of the transmitting and receiving antennae (antennas) so as to cover the transmitting and receiving antennae.
The radio wave sensor described in Document 1 is configured to detect the presence of an object when the receiving antenna receives radio waves (reflected waves) that have been transmitted from the transmitting antenna to reflected by the object.
Here, with the radio wave sensor described in Document 1, there is a possibility that errors in detection will occur because part of the radio waves from the transmitting antenna may directly enter the receiving antenna depending on the strength of the electric field coupling between the transmitting and receiving antennae.